Known in the art is an internal combustion engine provided with an operating timing changing mechanism changing the operating timing of a valve of a cylinder of the internal combustion engine in accordance with the operating conditions etc. Further, as such an operating timing changing mechanism, one controlled by oil pressure is known. That is, for example, it is configured so that when advancing a valve operating timing, it supplies working oil through an advancing side oil path to an advancing oil pressure chamber and drains working oil through a retarding side oil path from a retarding oil pressure chamber so as to operate an oil pressure operating actuator and advance a rotational phase of a valve drive cam. Further, it is configured so that conversely when retarding a valve operating timing, it supplies working oil through a retarding side oil path to a retarding oil pressure chamber and drains working oil through the advancing side oil path from the advancing oil pressure chamber to operate the oil pressure operating actuator and retard the rotational phase of the valve drive cam.
Further, it is known to provide the advancing side oil path and retarding side oil path with valves able to act as check valves at any time to prevent the working oil from ending up flowing in reverse from the intended direction.
Further, known in the art is an internal combustion engine configured providing a valve camshaft driving operation mechanism of a valve of a cylinder of the internal combustion engine with not only valve drive cams, but also a pump drive cam so as to drive a fuel pump of the internal combustion engine. Further, when providing the valve camshaft with a pump drive cam in this way, the valve camshaft receives fluctuations in the reaction torque accompanying drive of valve operation (valve operation drive reaction torque) and also fluctuations in the reaction torque accompanying drive of the fuel pump (fuel pump drive reaction torque).
That is, more specifically, the valve operation drive reaction torque acts as torque in a direction inhibiting rotation of the valve camshaft (positive torque) since the valve spring is compressed in a period before a maximum position of cam lift for driving a valve in the opening direction during operation of the valve drive cam and acts as a torque in a rotating direction of the valve camshaft (negative torque) due to a springback force of the valve spring in a period after the maximum position of the cam lift for driving a valve in the closing direction. Further, the fuel pump drive reaction torque as well, in the same way as the valve operation drive reaction torque, acts as a torque in a direction inhibiting rotation of the valve camshaft (positive torque) in a period before the maximum position of the cam lift during operation of the pump drive cam and acts as a torque in a rotating direction of the valve camshaft (negative torque) in a period after the maximum position of the cam lift.
Further, the valve camshaft is acted on by a composite reaction torque of the valve operation drive reaction torque and the fuel pump drive reaction torque combined, but if the maximum value or amount of fluctuation of this composite reaction torque becomes larger, the torque required for driving the valve camshaft will become larger, the members transmitting power from the crankshaft to the valve camshaft (for example, the timing chain, timing belt, timing gear, etc.) will fall in lifetime, and other problems will arise.
Therefore, in the prior art, to deal with this problem, the practice has been to set the rotational phase of a valve drive cam and the rotational phase of the pump drive cam so as to flatten such a composite reaction torque and so that its maximum value becomes smaller or so that the amount of fluctuation of such a composite reaction torque becomes smaller (for example, see Japanese Patent Publication (A) No. 2001-227425, Japanese Patent Publication (A) No. 2006-207440, and Japanese Patent Publication (A) No. 2006-29093).